Electronic phase diagram of Fe${}_{1+y}$Te${}_{1-x}$Se${}_x$ revealed by magnetotransport measurements

Abstract

Among the Fe-based superconductors, Fe${}_{1+y}$Te${}_{1-x}$Se${}_x$ is unique in that its crystal structure is the simplest and the electron correlation level is the strongest, and thus it is important to investigate the doping($x$)-temperature ($T$) phase diagram of this system. However, inevitably incorporated excess Fe currently prevents the establishment of the true phase diagram. We overcome the aforementioned significant problem via developing a new annealing method termed as "Te-annealing" wherein single crystals are annealed under Te vapor. Specifically, we conducted various magnetotransport measurements on Te-annealed superconducting Fe${}_{1+y}$Te${}_{1-x}$Se${}_x$. We observed that crossover from the incoherent to the coherent electronic state and opening of the pseudogap occurs at high temperatures ($\approx$ 150 K for $x$ = 0.2). This is accompanied by a more substantial pseudogap and the emergence of a phase with a multi-band nature at lower temperatures (below $\approx$ 50 K for $x$ = 0.2) before superconductivity sets in. Based on the results, the third type electronic phase diagram in Fe-based high-$T_c$ superconductors is revealed.

10 pages, 5 figures, Proceedings of the International conference for ECSN-2019, Odessa, Ukraine

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Cited by in corpus (2)

• Enhanced superconducting pairing strength near a nonmagnetic nematic quantum critical point
• Onset Temperatures for Superconducting Fluctuations in Te-annealed FeTe${}_{1-x}$Se${}_x$ Single Crystals: Evidence for the BCS-BEC Crossover